Fascia for motor vehicles typically require superior impact characteristics. More particularly, these parts must be engineered to be sufficiently flexible and ductile so as to flex and return to their original shape without cracking in the event of predetermined front or rear vehicle impact. Thus, vehicle fascia typically must have a sufficiently high modulus, and must be sufficiently ductile to withstand standard impact tests.
Fascia are generally molded from a polyolefin material which is subsequently painted to match the other "Class A" finish exterior metal body components. It is easy to damage the pre-painted molded polyolefin parts during handling in the production facilities. This is particularly true during the frequent handling, which typically occurs between the molding operation and the paint ovens. The surface damage may not be noticed until the parts are painted with the typical high gloss exterior coatings. It is not possible to recycle the molded parts back into the molding process once they have been painted, and significant value is lost with each scrap part.
In the automotive industry, there is a continuing desire to reduce the amount of material used to manufacture vehicle body parts. In particular, it is desirable to provide parts that are of lesser weight, but of the same or better structural integrity. Reducing vehicle weight increases gas mileage and also helps meet environmental requirements. Moreover, reducing the amount of material used reduces material, energy, and other costs associated with part production.
With respect to motor vehicle fascia, it is desirable to provide a part having high impact resistant characteristics. For these applications, the dimensional stability is of lesser importance. Thus. for example, fascia can be more flexible (lower modulus) and have a higher coefficient of expansion than other body parts, such as outer door panels which are bounded on more than one side by other vehicle parts. In order to maintain the impact resistance, fascia are typically devoid of any substantial reinforcement. Because the fascia is not reinforced to any significant extent, they must be made thicker to provide the requisite dimensional stability. As the thickness of the fascia increases, more material costs are incurred. and the weight of the part is also increased. Heretofore, the thinnest fascia having sufficient dimensional stability so as to be commercially acceptable has had an average wall thickness of about 2.4 mm.